Thioamides

ABSTRACT

SULFENAMIDES CHARACTERIZED BY CARBONYL ADJACENT TO THE SULFENAMIDE NITROGEN, THE CHARACTERISTIC NUCLEUS OF WHICH IS   R-S-N(-)-CO-   WHERE THE DANGLING VALENCE ON THE NITROGEN MAY BE LINKED TO A SECOND CARBONYL, ALKYL, ARYL, CYCLOALKYL, HYDROGEN, ALKYLENE CARBON, OR ARYLENE CARBON, AND R IS ALKYL, ARYL, OR CYCLOALKYL. THE COMPOUNDS, MANY OF WHICH ARE NEW, INHIBIT PREMATURE VULCANIZATION OF VULCANIZABLE ELASTOMERS AND STABILIZE STYRENE-BUTADIENE RUBBER.

United States Patent Ofice 3,752,824 Patented Aug. 14, 1973 3,752,824 THIOAMIDES Aubert Yancher Coran, Creve Coeur, Mo., and Joseph Edward Kerwood, St. Albans, W. Va., assignors to Monsanto Company, St. Louis, M0.

N0. Drawing. Division of application Ser. No. 714,445,

Mar. 20, 1968, now Patent No. 3,546,185, and a continuation-in-part of applications Ser. Nos. 549,730, May 12, 1966, 579,493, Sept. 15, 1966, and 459,466, May 27, 1965, all now abandoned. This application Mar. 27 1970, Ser. No. 29,717

Int. Cl. C07d 27/30 US. Cl. 260326 S 16 Claims ABSTRACT OF THE DISCLOSURE Sulfenamides characterized by carbonyl adjacent to the sulfenarnide nitrogen, the characteristic nucleus of which is where the dangling valence on the nitrogen may be linked to a second carbonyl, alkyl, aryl, cycloalkyl, hydrogen, alkylene carbon, or arylene carbon, and R is alkyl, aryl, or cycloalkyl. The compounds, many of which are new, inhibit premature vulcanization of vulcanizable elastomers and stabilize styrene-butadiene rubber.

CROSS REFERENCES TO RELATED APPLICATIONS This application is a division of application Ser. No. 714,445, filed Mar. 20, 1968, now US. 3,546,185, granted Dec. 8, 1970, a continuation-in-part of the application Ser. No. 579,493, filed Sept. 15, 1960, now abandoned, a continuation-in-part of the application Ser. No. 549,730, filed May 12, 1966, now abandoned, and a continuation-in-part of the application Ser. No. 459,466, filed May 27, 1965, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to an improved vulcanizing process for rubber and to the rubber stocks obtained by using this improved process. The invention relates to improved accelerator-inhibitor combinations for rubber. The invention also relates to new compounds useful as inhibitors of premature vulcanization in rubber. More particularly, the invention relates to a method for preventing the premature vulcanization of rubber stocks and to the rubber stocks obtained by using this method.

In the manufacture of vulcanized rubber products, crude rubber is combined with various other ingredients such as fillers, accelerators, and antidegradants to alter and improve processing of the rubber and to improve the properties of the final product. The crude rubber is put through several steps in the plant before it is ready for the final step of vulcanization. Generally the rubber is mixed with carbon black and other ingredients except the vulcanizing agent and accelerator. Then the vulcanizing and accelerating agents are added to this masterbatch in a Bambury mixer or a mill. Scorching, viz, premature vulcanization, can occur at this stage of the processing, during the storage period befor vulcanizing, and during the actual vulcanization. After the vulcanizing and accelerating agents are added, the mixture of crude rubber is ready for calendering or extruding and vulcanization. If premature vulcanization occurs during the storage of the crude mixture or during processing prior to vulcanization, the processing operations cannot be carried out because the scorched rubber is rough and lumpy, consequently useless. Premature vulcanization is a major problem in the rubber industry and must be prevented in order to allow the rubber mix to be preformed and shaped before it is cured or vulcanized.

There are several reasons offered for premature vulcanization. The discovery of the thiazolesulfenamide accelerators constituted a major breakthrough in the vulcanization art because thiazolesulfenamides delayed onset of the vulcanizing process, but once it started'the built-in amine activation of the thiazole resulted in strong, rapid curing. Mercaptobenzothiazole is a valuable organic vulcanization accelerator but by present standards would be considered scorchy. It has been largely replaced by the delay-action accelerators, but further improvement has eluded the art. The development of high pH furnace blacks which lack the inherent inhibiting effect of the acidic channel blacks and the popularity of certain phenylenediamine antidegradants which promote scorching have placed increasingly stringent demands on the accelerator system.

Retarders have long been available to rubber compounders. These include N-nitrosodiphenylamine, salicyclic acid, and a terpene-resin acid blend. See Editors of Rubber World, Compounding Ingredients for Rubber, 91-94 (3rd ed., 1961). Acids as retarders are generally ineffective with thiazolesulfenamide accelerators or adversely afiect this vulcanizing process. Nitrosoamines as retarders are only of limited elfectiveness with thiazolesulfenamides derived from primary amines. Certain sulfenamides which are not accelerators per se have been shown to retard mercaptobenzothiazole and other scorchy accelerators, but the eifect on another sulfenamide incorporated as the primary accelerator has been marginal. Similarly, mixtures of accelerating sulfenamides have been proposed as a means of improving processing safety, but neither of these innovations has significantly improved a good delay-action. accelerator.

Some of the inhibitors of the invention have vulcanizing and accelerating properties in their own right. For example, Belgian Pat. 619,219 (1962) to US. Rubber discloses N-[(trichloromethyl)thio]maleimide as a vulcanizing agent. The sulfur-vulcanizing agents, accelerators, and antidegradants used in the combinations of this invention do not include the inhibitors of the invention. A combination of an accelerator and an inhibitor of this invention. A combination of an accelerator and an inhibitor of this invention is an improved rubber additive which allows longer and safer processing time for rubber.

SUMMARY OF THE INVENTION We have discovered a class of sulfenamides which are extremely valuable inhibitors of premature vulcanization. These are characterized by the presence of a carbonyl group adjacent to the sulfenamide nitrogen. The characteristic nucleus is O RS-N-Jiwhere the dangling valence on the nitrogen may be linked to a second carbonyl, alkyl, aryl, cycloalkyl, hydrogen, alkylene carbon, or arylene carbon and R is alkyl, aryl, or cycloalkyl. Aryl is used in the usual generic sense to mean any univalent organic radical where free valence belongs to an aromatic carbocyclic nucleus and not to a side chain. The term includes radicals substituted in the carbocyclic nucleus, for example, by alkyl, alkoxy, nitro, chloro, bromo, fluoro, iodo, and hydroxy. It is preferred that the carbocyclic nucleus contain not more than one electronegative substituent. Alkyl is used in the usual sense to mean univalent aliphatic radicals of the series C H Primary, secondary, and tertiary alkyls are included, for example, straight or branched chains. However, primary and secondary alkyl of 1 to 20 carbon atoms are the preferred alkyl compounds of this invention. The term cycloalkyl includes cycloalkyl radicals of 5 to 12 carbon atoms in the ring. Carbon atoms of the heterocyclic nuclei which contain hydrogen can be substituted by alkyl, alkoxy, nitro, chloro, bromo, fluoro, iodo, and hydroxy, for example, 1,3-bis(phenylthio)-5-chloro-2-benzimidazolinone.

An object of this invention is to promote the progress of .science and useful arts. An object of this invention is to provide a method to eflectively prevent the premature vulcanization of rubber. A further object of this invention is to provide new chemical compounds useful as premature vulcanization inhibitors especially with delayed-action thiazolesulfenamides. A further object of this invention is to provide a method for a faster rate of cure for vulcanizable rubber without premature vulcanization. A further object of this invention is to provide a method to increase the available processing time prior to the actual vulcanization of rubber. A further object of this invention is to provide a method to prevent the premature vulcanization of crude rubber in storage containing a vulcanizing and accelerating agent. A further object of this invention is to provide a method to prevent the premature vulcanization of rubber during the actual vulcanization step. A further object of this invention is to prevent the premature vulcanization of rubber at any time. A further object of this invention is to provide a safer method for processing and vulcanizing rubber. A further object of this invention is to provide a stabilizer for rubber. A further object of this invention is to provide new and improved vulcanized rubber products. A further object of this invention is to provide a vulcanized rubber stock in which the rate of reversion is reduced. Other objects of the invention will become apparent as the description of our invention proceeds. These objects are accomplished by using a sulfenamide derived from an amide or imide in the processing of rubber.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Our invention is that compounds having the formula are excellent premature vulcanization inhibitors for a vulcanizable diene rubber where R and R with the carbonyl and nitrogen atom constitute a radical, for example,

N-phthalimidyl,

N-succinimidyl,

N-adipimidyl,

N-glutarimidyl,

N-3,3-dirnethylglutarimidyl,

N-hexahydrophthalimidyl,

7-oxabicyclo[2.2.1]heptane-Z,3-dicarboximid-N-yl,

7-oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboximid-N-yl,

tetrapropenylsuccinimid-N-yl,

methylsuccinimid-N-yl,

octadecylsuccinimid-N-yl,

n-decenylsuccinimid-N-yl,

1,4,5,6,7,7-hexachlorobicyclo [2.2. l he pt-5-ene-2,3-

dicarboximid-N-yl,

5 ,5 -dimethyl-3-hydantoinyl,

hydantoinyl,

5 ,5 -dipheny1-3-hydantoinyl,

N-maleimidyl,

4-cyclohexene-1,2-dicarboximid-N-yl,

2-benzimidazolinon-1-yl,

2-benzothiazolinon-N-yl,

3-arylthio-2-benzimidazolinon-l-yl,

3-alkylthio-2-benzimidazolinonl-yl,

3-cycloalkylthio-2-benzimidazolinonl-yl Z-imidazolinonl-yl,

3-cycloa]kylthio-Z-imidazolinonl -yl,

More specific examples of R" are CCl methyl, ethyl, propyl, isopropyl, butyl, amyl, t-butyl, phenyl, benzyl, chlorophenyl, nitrophenyl, tolyl, naphthyl, cyclooctyl, cyclopentyl, and cyclododecyl.

The premature vulcanization inhibitors of this invention include compounds of the formula II I RCNSR where constitutes a radical, for example,

N- (arylthio carbamoyl,

N- (cycloalkylthio carbamoyl, N- (alkylthio carb amoyl, N-arylcarbamoyl,

N-alkylcarb amoyl, and N-cycloalkylcarbamoyl,

and R is alkyl, aryl, or cycloalkyl. More specific examples of N- chlorophenylthio carbamoyl, N- (chlorophenylthio carbamoyl, N- benzylthio carbamoyl,

N- tolylthio carbamoyl,

N- (methylthio carb amoyl,

N- (ethylthio carbamoyl,

N- (propylthio) carbamoyl,

N- (isopropylthio) carbamoyl,

N- t-butylthio carbamoyl, N-phenylcarbamoyl, N-methylcarbamoyl, N-ethylcarbamoyl, N-propylcarbamoyl, N-isopropylcarbamoyl, N-t-butylcarbamoyl, N-trichloromethylcarbamoyl, N-benzylcarbamoyl, N-nitrophenylcarbamoyl, N-chlorophenylcarbamoyl, and N-tolylcarbamoyl,

and more specific examples of R are methyl, ethyl, propyl, isopropyl, t-butyl, trichloromethyl, phenyl, benzyl, chlorophenyl, tolyl, nitrophenyl, naphthyl, sec. butyl, n-butyl, namyl, n-hexyl, n-heptyl, 2-ethylhexyl, n-octyl, n-decyl, nundecyl, n-dodecyl, n-tridecyl, o-tolyl, p-tolyl, m-tolyl, pethylphenyl, p-isopropylphenyl, cyclooctyl, cyclopentyl, and cyclododecyl.

N (cyclohexylthio) adipimide,

7 N-(propylthio)bicyclo[2.2.1]hept--ene-2,3-dicarboximide, 1,4,5 ,6,7,7-hexachloro-N- isopropylthio) bicyclo- [2.2.1]hept-5-ene-2,3-dicarboximide, 1,4,5 ,6,7,7-hexachloro-N- (n-dodecylthio bicyclo [2.2.1

hept-5-ene-2,3-dicarboximide, N-(cyclohexylthio)-4-cyclohexene-1,2-dicarboximide, N- (cyclooctylthio -4-cyclohexene-1,2-dicarboximide, N- (phenylthio) -4-cyclohexene-1,2-dicarboximide, N- (chlorophenylthio -4-cyclohexene-1,Z-dicarboximide, -N- (benzylthio -4- cyclohexene- 1 ,Z-dicarboximid e, N- (tolylthio) -4-cyclohexene-1,Z-dicarboximide, N- (nitrophenylthio) -4-cyclohexene-1,2-dicarboximide, N- (t-butylthio) -4-cyclohexene-1,Z-dicarboximide, N- (methylthio) -4-cyclohexene-1,2-dicarboximide, N-(ethylthio) -4-cyclohexene-1,2-dicarboximide, N- (propylthio) -4-cyclohexene-1,2-dicarboximide, N-(n-dodecylthio)-4-cyclohexene-'1,Z-dicarboximide, N-(isopropylthio)-4-cyclohexene-1,2-dicarboximide, and N,N'-bis (ar-tolylthio) -1,2,4,S-benzenetetracarboxylic- 1,2 4,5-diimide.

'Further examples of the compounds useful as premature vulcanization inhibitors in this invention are N- (naphthylthio )phthalimide, N- n-butylthio) succinimide, N- methylthio) succinimide, N- (ethylthio) succinimide, N- (propylthio) succinimide, N-(isopropylthio) succinimide, N-(cyclohexylthio)succinimide, and N- (cyclooctylthio) succinimide; 1,3 -bis (n-hexylthio) -1,3 -dicyclohexyl-ure a, N-phenyl-N'- (phenylthio )urea, N-phenyl-N'- (methylthio) urea, N- phenyl-N'- (ethylthio urea, N-pheny1-N'-(propylthio urea, N-phenyl-N- (isopropylthio) urea, N-phenyl-N'- (t-butylthio) urea, N-phenyl-N'- (n-dodecylthio urea, N-phenyl-N'- cyclohexylthio urea, N-phenyl-N- cyclooctylthio) urea, N-methyl-N'- (phenylthio) urea, N-ehtyl-N'- (phenylthio urea, N-propyl-N- (phenylthio )urea, N-isopropyl-N'- (phenylthio urea, N-t-butyl-N- (phenylthio urea, N-cyclooctyl-N'- (phenylthio) urea, N-cyclohexyl-N-(phenylthio urea, N-n-dodecyl-N'- (phenylthio) urea, and variations thereof;

and N- cyclo dodecylthio) succinimide.

Rubber stocks containing delayed-action accelerators can be used in the process of this invention. Cheaper, more scorchy accelerators can also be used with an excellent degree of improvement. The improved vulcanizing process of this invention can be used advantageously to process stocks containing furnace blacks as well as stocks containing other types of blacks and fillers used in rubber compounding. The invention is also applicable to gum stocks.

Our invention is applicable to rubber mixes containing sulfur-vulcanizing agents, peroxide-vulcanizing agents, organic accelerators for vulcanization, and antidegradants, none being the inhibitor used. For the purposes of this invention, sulfur-vulcanizing agent means elemental sulfur or sulfur containing vulcanizing agent, for example, an amine disulfide or a polymeric polysulfide. The invention isapplicable to vulcanization accelerators of various classes. Forexample, rubber mixes containing the arcmatic thiazole accelerators which include benzothiazyl-Z- monocyclohexylsulfenamide, 2 mercaptobenzothiazole, N-tert-butyl 2 benzothiazole sulfenamide, 2-benzothiazolyl diethyldithiocarbamate, and 2 (morpholinothio) bengothiazole can be used. Amine salts of mercaptobenzothiazole accelerators, for example, the t-butyl amine salt of mercaptobenzothiazole, like salts of morpholine, and 2,6-d'imethyl morpholine, can be used in the invention. Thiazole accelerators other than aromatic can be used. Stocks containing accelerators, for example, the tetramethylthiuram disulfide, tetramethylthiuram monosulfide, aldehyde amine condensation products, thiocarbamylsulfenamides, thioureas, xanthates, and guanidine derivatives, are substantially improved using the process of our invention. Examples of thiocarbamylsulfenamide accelerators are shown in US. Pats. 2,381,392, Smith assigned to Firestone, 2,388,236, Cooper assigned to Monsanto, 2,424,921, Smith assigned to Firestone, and Britain Pat. 880,912, Dodson assigned to Imperial Chemical Industries Limited. The invention is applicable to accelerator mixtures. The invention is applicable to stocks containing amine antidegradants. Rubber mixes containing antidegradants, for example, N-1,3-dimethylbutyl-N'-phenylp-phenylenediamine, N,N' bis(1,4 dimethylpentyl)-pphenylenediamine, and other phenylenediamines, ketone, ether, and hydroxy antidegradants and mixtures thereof, are substantially improved using the process of our invention. Mixtures of antidegradants, for example, a mixture of N-l,3-dimethylbutyl-N-phenyl p phenylenediamine and N,N-bis( 1,4 dimethylpentyl)-p-phenylenediamine, furnish a much improved final product when used with the inhibitors of this invention.

The inhibitors of our invention can be used in natural and synthetic rubbers and mixtures thereof. Synthetic rubbers that can be improved by the process of this invention include cis-4-polybutadiene, butyl rubber, ethylenepropylene terpolymers, polymers of 1,3-butadiene, for example, 1,3-butadiene itself and of isoprene, copolymers of 1,3-butadiene with other monomers, for example, styrene, acrylonitrile, isobutylene, and methyl methacrylate. The invention relates to diene rubbers, and the terms rubher and diene rubber are synonymous for the purpose of this invention.

The new compounds of this invention are prepared as follows:

To prepare N,N'-di(phenylthio)urea, a solution of 6.0 grams (0.1 mole) of urea and 25.0 grams (0.25 mole) of triethylamine in 200 ml. of DMF is cooled to 10 C. in a three-necked 500 ml. flask equipped with a mechanical stirrer and thermometer. To this solution is added slowly 28.8 grams (0.2 mole) of benzene sulfenyl chloride dissolved in 77 ml. carbon tetrachloride. During the addition the temperature is allowed to increase to 5 C. and a slurry of the triethylamine salt forms. This slurry is transferred to a 4.0 liter beaker and the product is precipitated by the addition of 3.0 liters of ice water with vigorous stirring. The brown solid is collected by filtration and upon recrystallization from ethanol yields a tan powder which melts at 104105 C. Analysis of the product shows 9.58% nitrogen and 23.13% sulfur. Calculated percentages for C H N OS are 9.60% nitrogen and 22.00% sulfur. The infrared spectrum is consistent with the proposed structure. The new ureas listed, supra, are prepared in a similar manner with comparable results.

N-(phenylthio)maleimide is prepared in the following manner: 14.4 grams of benzene sulfenyl chloride is added slowly at 1520 C. to a mixture of 9.8 grams (0.1 mole) of maleimide and 20.0 grams (0.2 mole) of triethylamine dissolved in 200 ml. of dry benzene in a threenecked 500 ml. reaction flask equipped with a mechanical stirrer and thermometer. The reaction mixture is allowed to stir until it reaches room temperature. This requires about 30 minutes. The triethylamine salt is collected by filtration, and the cake is washed with ml. of benzene. The filtrate is evaporated under reduced pressure until the product starts to precipitate from solution; The slurry is transferred to a 4.0 liter beaker and 3.0 liters of heptane is added with vigorous stirring. This precipitates the remaining product which is collected by filtration and washed with cold heptane. The product is allowed to dry overnight at room temperature. There is obtained 12.0 grams of product which, upon recrystallization from ethanol, has a melting point of 81-82 C. The infrared spectrum is consistent with the proposed structure. The new maleimides listed, supra, are prepared in a similar manner with comparable results.

N (phenylthio) 4 cyclohexene-l,2-dicarboximide is prepared in the following manner: 14.4 grams (0.1 mole) of benzene sulfenyl chloride dissolved in 30.0 grams of carbon tetrachloride is added slowly to a mixture of 14.9 grams (0.1 mole) of 4cyclohexene-1,2-dicarboximide and 12.0 grams (0.12 mole) of triethylamine in 250 ml. of benzene at 15 C. in a 500 ml. three-necked flask equipped with a stirrer and thermometer. The temperature is controlled at 15 C. with external cooling during the addition of the benzene sulfenyl chloride. The reaction is then allowed to warm to room temperature and the triethylamine salt is removed by filtration, washed with a small amount of benzene and 200 ml. of heptane is added to the filtrate to precipitate the product. The benzene and heptane are removed under reduced pressure. There is obtained 25.2 grams of a white solid which melts at 105 108 C. The product is recrystallized from carbon tetrachloride and has a melting point of 121- 122.5 C. Analysis shows 5.29% nitrogen and 11.69% sulfur. Calculated percentages for C H N'O S are 5.42% nitrogen and 12.39% sulfur. The new 4-cyclohexene-l,2- dicarboximides listed, supra, are prepared in a similar manner with comparable results.

The new 5,5-dimethylhydantoins and 1,4,5,6,7,7-hexachlorobicyclo[2.2.l] hept-5-ene-2,3-dicarboximides listed, supra, are prepared in a similar manner to N-(phenylthio)-4-cyclohexene1,2-dicarboximide with comparable results.

N (phenylthio)bicyclo[2.2.1] hept 5-ene-2,3-dicar boximide is prepared in the following manner: To a mixture of 16.3 grams (0.1 mole) of the imide of bicyclo- [2.2.1] hept-5-ene-2,3-dicarboxylic anhydride and 11.1 grams (0.11 mole) of triethylamine in 300 ml. of benzene, there is added dropwise with stirring 0.105 mole of benzene sulfenyl chloride as a carbontetrachloride solution over a 30 minute period. The temperature of the mixture is maintained at 30 C. during the addition. The reaction mixture is stirred an additional minutes after the sulf ny1 chloride solution is added. The reaction mixture is filtered to remove triethylamine hydrochloride and the filtrate is added to 3.5 liters of chilled heptane. A white solid is obtained weighing 17.6 grams. A sample of the N (phenylthio)-bicyclo[2.2.1] hept-5-ene-2,3-dicarboximide melts at 123 -125 C. Analysis shows 5.37% nitrogen and 11.09% sulfur. Calculated percentages for C H NO' S are 5.16% nitrogen and 11.80% sulfur. N- phenylthionaphthalimide, N phenylthio 3,4,5,6 tetrachlorophthalimide, N phenylthio 3,4,5,'6 tetrabromophthalimide, and similar compounds are prepared in a similar manner to N-(phenylthio)-bicyclo[2.2.1] hept-S- cue-2,3-dicarboximide with comparable results.

N,N' bis(phenylthio) 1,2,3,4 benzenetetracarboxylic-1,2:4,5-diimide is prepared in the following manner: To a solution of 21.6 grams (9.1 moles) of pyromellitic bis-dicarboximide and 22.2 grams (0.22 mole) of triethylamine in 300 ml. of dimethylformamide, there is added dropwise with stirring 0.21 mole of benzene sulfenyl chloride as a carbontetrachloride solution. The temperature is maintained at to C. Three liters of ice water is added to the resulting slurry to precipitate the product. The N,N'bis(phenylthio)-1,2,4,5-benzenetetracarboxylic-1,2:4,5-diimide product is a yellow solid. A sample of the product melts at 260 C. Analysis of the product shows 6.05% nitrogen and 14.60% sulfur. Calculated percentages for C 2H N O S are 6.48% nitrogen and 14.82% sulfur. N,N-bis(ar-tolythio)-1,2,4,5-benzenetetracarboxylic-1,2:4,5-diimide and similar compounds are prepared in a similar manner with comparable results.

N-(cyclohexylthio)glutarimicle is prepared in the following manner: Twenty grams (0.177 mole) of glutarirnide is added in one portion to a mixture of 24 grams (0.24 mole) of triethylamine and 200 ml. of dimethylformamide. To the resulting solution, 26.5 grams (0.177 mole) of cyclohexylsulfenyl chloride dissolved in 150 ml. of n-pentane is added dropwise over a 30 minute period. The temperature of the reaction increases from about 23 C. to 40 C. during the addition. The resulting slurry is stirred for an additional 30 minutes and then transferred to a 3.0 liter beaker. Two liters of cold water is then added to the slurry with vigorous stirring, and a light tan precipitate is formed. The solid is collected by filtration and allowed to dry at room temperature. The tan solid is recrystallized twice from heptane to yield long white needles which melt at 83 -85 C. Analysis of the product shows 13.70% sulfur and 6.02% nitrogen. Calculated percentages for C H NO S are 14.13% sulfur and 6.16% nitrogen.

Other glutarimides and 3,3-dimethylglutarimide compounds of this invention are prepared in a similar manner with comparable results. Analysis of N-(cyclohexylthio)-3,3-dimethylglntarimide shows 12.25% sulfur and 5.34% nitrogen. Calculated percentages for C H NO S are 12.57% sulfur and 5.5% nitrogen.

The following tables illustrate the invention in greater detail and the best mode for carrying it out, but are not to be construed as to narrow the scope of our invention. For all the rubber stocks tested and described, infra, as illustrative of the invention, Mooney scorch times at 121 C. and 135 C. are determined by means of a Mooney plastometer. The time in minutes (i required for the Mooney reading to rise five points above the minimum viscosity is recorded. Longer times are indicative of the activity of the inhibitor. Longer times on the Mooney Scorch Test are desirable because this indicates greater processing safety. Percentage increases in scorch delay are calculated by dividing the Mooney scorch time of the stock containing the premature vulcanization inhibitor by the Mooney scorch time of the control stock, multiplying by 100', and subtracting 100. These increases show the percentage improvement in scorch delay over the control stock which contains no inhibitor. Additionally, cure ratings are calculated from the time required to cure the stocks at 144 C., and in some cases 153 C. Curing characteristics are determined by means of the Monsanto Oscillating Disc Rheometer described by Decker, Wise, and Guerry in Rubber World, December 1962, page 68. From the Rheometer data, R.M.T. is the maximum torque in Rheometer units, or t is the time in minutes for a rise of three or two Rheometer units, respectively, above the minimum reading and is the time required to obtain a torque 90% of the maximum.

The trademarks of some compounds used in the practice of this invention are Santocure MOR, Santofiex 77, Santocure NS, DPG, Thiofide, and Vultrol. Santocure MOR is the accelerator 2-(morpholinothio)benzothiazole. Sant-oflex 77 is the antidegradant N,N-bis(1,4-dimethylpentyl)-p-phenylenediamine. Santocure NS is the accelerator N-tert-butyl-2-benzothiazolesulfenamide. DPG is an accelerator reported to be diphenylguanidine. Thiofide is an accelerator reported to be benzothiazyl disulfide. Vultrol is a vulcanization retarder reported to be N-nitrosodiphenylamine.

Table I illustrates the results of using N- (phenylthio)- succinimide and N-(benzylthio)succinimide as premature vulcanization inhibitors in stocks of natural rubber containing the antioxidant Santoflex 77 and the accelerator Santocure MOR. From the data ofTable I it will be noted that N-(phenylthio)succinimide and N-(benzylthio)succinimide are quite active in the presence of the accelerator as premature vulcanization inhibitors. From the intermittent ozone test, there appears to be no effect on the ozone resistance of the vulcanizates containing the inhibitors.

TABLE I Stank A B Natural rubber 100 100 100 High abrasion furnace black 50 50 50 Zinc oxide 5 5 Stearic acid 3 3 3 Hydrocarbon softener 10 10 Sulfur 2. 5 2. 5 2. 5 Santoflex 77- 3 3 3 Santocure MOR. 0. 5 0. 5 0. 5 N-(phenylthio) r 1. 0 N-(benzylthio)succinimide 1. 0

tas-s 4. 1 4.6 4.5 Percent increase in scorch delay 111 95 Shore A hardness"; 58 --60 58 Modulus 300, 13.5.1. 1900 1930 1930 Ultimate tensile strength, p.s.i- 3600 3600 3600 Ultimate elongation. percent 490 490 480 Rheometer at 144 0.:

tan. 19.0 26. 2 26. 8

k2 173 173 165 Intermittent ozone: 1

Hours 90% retention 16 13 Hours 80% retention 31 30 32 1 k is a specific rate constant measured in reciprocal minutes. See

Goran, 37 Rubber Chemistry and Technology 689 (1964).

phenyl p-phenylenediamine-i-N-(phenylthio)succinimide (0.25 part).

11 Santocure NS+N 1,3 dimethylbutyl-N'- phenyl p-phenylenediamine+N-(pheny1thio)succinimide (0.5 part).

12 SantOcurc NS+N 1,3 dimethylbutyl-N'- phenyl p-phenylenediamine+N-(phenylthio)succinimide (1.0 part).

Results comparable to the natural rubber preparations of Table II are obtained using cis-4-polybutadiene, butyl rubber, ethylenepropylene terpolymers, polymers of 1,3- butadiene, for example, 1,3-butadiene itself and of isoprene and copolymers of 1,3-butadiene with other monofunctions as an inhibitor in natural rubber with Santocure NS as well as it did with the accelerator Santocure MOR. It is also shown in Table H that 0.25 part per hundred N- mers, for example, styrene, acrylonitrile, isobutylene, and methyl methacrylate as the base stock and N-(phenylthio)succinimide and N-(benzylthio)succinimide as the inhibitor. For example, Table III shows the premature vulcanization inhibitor properties of N-(phenylthio)succinimide in a styrene-butadiene rubber B-'5 masterbatch. The compound is compared with Vultrol in several sys- TABLE II Stork 1 2 3 4 5 6 7 8 9 10 11 12 Mooney scorch at 121 0.213s 20- 3 3- 0 9 7- 5 32- 7 43. 0 40. 6 48. 6 37. 6 47. 4 5 Percent increase in scorch delay. 38. 0 11. 0 37. O 80. 0 20. 0 26. 0 43.2 g Rheometer at 144 0.:

(phenylthio)succinimide with Santocure NS has about the same vulcanization characteristics as 1.0 part per hundred of the well-known retarder Vultrol with Santocure MOR. It is shown that increasing concentrations of N-(phenylthio)succinimide with Santocure NS does not inhibit the rate of crosslink formation as measured by the specific rate constant k The parameter k is actually increased with increasing amounts of N-(phenylthio)succinimide in the presence of the phenylenediamine antidegradants. Stocks containing N-(pheny1thio)succinimide and Santocure NS also show an excellent rate of cure after the onset of vulcanization.

The code for Table H is as follows. The stocks contain:

Parts Natural rubber 100 High abrasion furnace black 50 Zinc oxide 5 Stearic acid 3 Hydrocarbon softener 3 Antidegradant 3 Accelerator 0.5 Premature vulcanization inhibitor As indicated Sulfur 2.5

Twelve stocks were tested. The stocks include the following:

phenyl-p-phenylenediamine.

terns. The code for Table III is as follows. A B-5 masterbatch is composed of:

Parts Oil-extended styrene-butadiene rubber containing 37.5% highly aromatic oil Intermediate super Abrasion furnace black 68.5. Zinc oxide 3.0. Stearic acid 2.0. The stocks also contain:

Antidegradant N-l,3-dimethylbutyl N phenyl-p-phenylenediamine 3.0. Premature vulcanization inhibitor As indicated below. Accelerator 1.2 or as indicated below. Sulfur 2.0.

Ten stocks were tested. The stocks include the following:

TABLE III Stock 1 2 3 4 5 6 7 8 10 Mooney scorch at 135 0.: t5 26. 9 20. 6 30. 20. 8 24. 3 26. 31. 0 39. 0 10. 0 19. 5 Percent increase in scorch delay 11. 0 0 18. 0 29. 0 50. 0 45. 0 95. 0 Rheometer at 153 0.:

Vultrol, the known inhibitor, shows a mere 11% increase TABLE VI in scorch delay with Santocure MOR and no increased delay with Santocure NS. But the compound of our invention, at the same concentrations, shows a 45% increase in scorch delay with Santocure MOR and a 50% increase with Santocure NS in styrene-butad'iene rubber.

Table IV shows the premature vulcanization inhibitor properties of N- (phenylthio)succinimide in natural rubber when a peroxide vulcanizing agent is used, N-(phenylthio)succinimide shows a 57% increase in scorch delay with the vulcanizing agent dicumyl peroxide. The masterbatch for Table IV is composed of:

Parts Smoked sheets 100 High abrasion furnace black 50 Zinc oxide 5 Stearic acid 3 Hydrocarbon softener 10 Total parts 168 TABLE IV Masterhatoh 168 168 N-1,3-dimethylbuty1-N -phenyl-p-pheny1enediamine 1. 5 1. 5 Dicumyl peroxide 2. 0 2. 0 N-(phenylthinl nnoinimide L 0 Mooney scorch at 135 0.22s .1 4. 9 7. 7 Percent increase in scorch delay 57 Table V shows the results of tests on N-(phenylthio) succinimide, N-(t-butylthio)phthalimide, N,N'-di(phenylthio)urea, 1,3-bis(phenylthio)-2-imidazolinone and N- (phenylthio)maleimide as premature vulcanization inhibitors in rubber. N-(phenylthio)maleimide gives a 174% increase in scorch delay over the control. The rubber mixture of the test is an A-6 masterbatch. An A-6 masterbatch is composed of the following.

Parts Smoked sheets 100 High abrasion furnace black 50 Zinc oxide I 5 Stearic acid 3 Hydrocarbon softener 10 Total parts 168 All stocks contain three parts Santoflex 77, 0.5 part Santocure MOR, and 2.5 parts sulfur.

Comparable results are obtained when the accelerator Santocure NS and the antidegradant N-1,3-dimethylbutyl- N'-pheny1-p-phenylenediamine or a mixture of this antidegradant and Santoflex 77 are used. Table VI shows N- (phenylthio)maleimide as a scorch inhibitor in a B-S masterbatch of styrene-butadiene rubber.

N (phenylthio)maleimi de 1. 0 N-l, 3-dimethylbutyl-N phenylp phenylenediamine 2 2 2 2 uliur 1. 7 1. 7 1. 7 1. 7 Mooney scorch at; 135 C 10. 4 22. 8 22. 8 41. 8 Percent increase in scorch delay. 119 83 Rheometer at 153 C Parts C1s-4-polybutadiene Aromatic extender and process oil 8 Stearic acid 2 Santoflex 77 3 Zinc oxide 3 Intermediate super abrasion furnace black 50 TABLE VII Masterbatch 166 166 166 166 1, 3-bis (trlchloromethylthio-Z-benzhnidazolinone. 1. 0 N-(phenylthio) succi de 1. 0 1, 3-bis (phenylthio)-2-bonzimidazolinone- 1. 0 Santocnre MO R 0. 6 0. 6 0. 6 0. 6 Sulfur 2. 4 2. 4 2. 4 2. 4 Mooney scorch at (3.25...- 15. 5 17. 7 20.3 22. 8 Percent increase in scorch delay- 14 31 47 Rheometer at 153 0.:

R.M.T 58. 0 78. 0 61. 2 57. 2 t2 7. 6 8. 3 8. 6 9. 8 he 15. 7 19. O 17. 5 13. 2

Parts Ethylene-propylene terpolymer 100 High abrasion furnace black 80 Zinc oxide 5 Naphthenic-type oil plasticizer and softener 40 TABLE VIII TABLE XII Masterbateh 225 225 225 BtOOk 1 2 3 4 5 Tetramethyl thiuram monosulfide. 1. 5 1. 5 1. 5 Mercaptobenzothiazole 0. 5 0. 5 0. 5 A-l masterbatch 161 161 161 161 161 N-(phenylthio)succinimide 1 3 3 3 3 3 1,3-bis (phenylthio)benzimidazolinone 1. 0 0. 5 0. 5 0. 5 0. 5 0. 5 Sulfur 1.5 1 5 1.5 r 2.5 2.5 2.5 2.5 2.5 Mooney scorch at 135 0.: t5 min. 10. 9 14. 9 20. 5 N-[(trichlor0methyl)thio]-4 Percent in scorch delay 28 80 cyclohexene-I,2-diearboxirnlde 1. 0 Rheometer at 100 0.: 5,5-dimethyl-3-[(trichloromethyl)- R.M 63.5 60.0 58.0 thio1hydantoin 1.0

1L 4. 6 6.0 7. 5 N-[(trichl0romethyl) thio]-maleimide 1. 0

tun 11.7 15.2 17.5 10 1,3-bis(trichl0r0methy1thio)-2- benzimidazolinon 1. 0 gloone giscorch at1121 0.2155 18.3 30.8 34.3 30.0 39.4 N-phenyl-N'-(phenylthio)urea was tested in an A-6 gggg gf gfii f delay 6&0 115-0 masterbatch as a premature vulcanization inhibitor and R.M.T 7%: 76.3 79.2 75.5 22.5 9. 10. 9.9 12.6 shows a 97% increase n scorch delay over the control. 17's 1&7 206 2&0 2 The results are reported in Table IX. 15

TABLE IX A-G masterbatch 168 168 A material composed of N-[(trichloromethyl)thio]-4- ggifg 3:2 cyclohexene-1,2-clicarboximide, 50% active on an inert Santoflex 77. 3.0 3.0 0 clay filler, shows comparable results to the compound fig gggfi gfigfi gfgl g?$33 'g kg per se when tested as a premature vulcanization inhibitor. Percent increase in scorch delay 97 Tables XIII and XIV ShOW that the compound N- (cyclohexylthio)glutarimide, N-(cyclohexylthio) 3,3-di- Comparable results are obtained when the other unsymmethylglutanmldez N.'(,Pheny1th)benzamlde are metrical ureas of the invention are tested as premature mateur vulcamzatlon mhibitors. The compounds are testvulcanization inhibitors ed in a masterbatch composed of:

Table X shows that 1,4,5,6,7,7-hexachloro-N-(trichlo- S k d h t 1 38 romethylthio)bicyclo-[2.2.1] hept 5 ene-2,3-dicarboxs ""g-f j "E -i 45 imide and 1,3 -bis(trichloromethylthio)-5,6-dichloro-2- grme. 6 Super 3 raslon mace ac 3 benzimidazolinone are effective premature vulcanization mc 1 inhibitors. Steam 2 Aromatic 011 plasticlzer 5 TABLE X A-l masterbatch 161 161 161 SantocureMOR- 0.5 0.5 0.5 TABLE X111 Sulfur 2.5 2.5 2.5 1,4,5,6,7,7-hexachloro-N-(trichloromethyl-thio) Sto 1 2 3 bicycl0[2.2.1]-hept-5-ene-2,3-diearboximido 1. 0 1,3-bis(trichloromethylthio)-5,6-dichl0ro-2- Mast rbatch 155 155 155 benzimirlmnli nnnn 1. 0 Sulfur- 2. 5 2. 5 2. 5 Mooney scorch at 121 0.:zs 30. 5 53. 0 51. 0 Santocure MO Rm. 0.5 0. 5 0. 5 Percent increase in scorch delay 74.0 67.0 N-l,3dlmethyll?utyl Rheometer at 144 Q; p-phenylenediamine.. 2 0 2. 0 2. 0

R.M.T 70. 1 70.0 70.0 N ycloh xylthio) glutar 1. 0

1L 7 9 12, 0 12, 2 N-(phenylthio) benzamide. 1. 0

t 23 0 39, 0 30, Q Mooney s corch at 121C; t 35. 2 85. 8 85. 3

Percent increase in scorch delay 144 144 Rheometer at 144 0.: 5 R.M.T 61.0 61. 2 63.8

Table XI shows that N-[(trichloromethyl)th1o]succ1nt 8.7 21.3 20.2 imide is a premature vulcanization inhibitor. With Santocure NS accelerator in the presence of the antidegradant N-1,3-dirnethylbutyl-N'-phenyl-p-phenylenediamine, this inhibitor improves the scorch delay about 43%. Com- TABLE XIV parable results are obtained when this antidegradant 1s qmk 1 2 replaced with Santoflcx 77.

ra s. 52 an ocure 0. TABLE XI th lb t lN h 1 n 1 drami 2' e y uyp eny-p-p anyone no. .0 1 2 3 4 5 6 55 Lb}-(cyclehexygthifloz3 3di;nethylglutarimide 0.5 ooney score a 21 0.5 g' gg 161 161 Percent increase in scorch dela 120.0 s t o'fi "6'5""6'5 Rheometer at 144 0.:

a RM. 09.3 67.2 Sulfur 2.5 2.5 2.5 2 5 2.5 2.5 h 8 9 17 2 N-[(trichloromethyl)thio] m 4 5 sueeinimide 1. 0 1. 0 1. 0 N 1,3-dimethylbutyl-N -phenyl- 6O p-phenylenediamine 3. 0 lzgoonm scorch at 121 23.1.--- 28.8 33.12 27 38 5 32 7 BICGH Increase In 500130 B BY Rheometer at 144 0.: Table XV lllustrates the use of 1,3-b1s(cyc1ohexylth1o)- E3 2-imidazolidinone, 1,3-bis(cyclohexylthio)hydantoin, and

39 1-cyclohexylthio-Z-imidazolidinone in a natural rubber masterbatch composed of the following: Parts Table XII shows that the compounds 1,3-b1s(tr1chloro- Natural rubber 100 methylthio) 2 benznnidazolinone, N-[(tr1chlorometh- Intermediata su er abrasion furnace black 45 yl)thio] 4 cyclohexene-1,2-dicarboximido, 5,5-dimeth- F St p 2 0 yl-3-[(trichloromethyl)thiOJhydantOin, and N-[(trichloa acl romethyl)thio1maleimide are premature vulcanization in- Hy rocarbon Softener "f 5 hibitors. In addition to the activity these compounds eX- Sulfur hibit as premature vulcanization inhibitors, the rheometer Santocllfe MOR tracings show that the rate of reversion during overcure Antldegradant 2.0 of natural rubber is reduced. Zinc oxide 3.0

TABLE XV Control 1,3-bis(cyclohexylthlo)-2-imidazolidi Table XVI shows that comparable results are obtained when the imide-moiety is benzimidazolinon-l-yl, benzothiazolinon-l-yl, or 'benzoxazolinon-l-yl, and that good results are obtained when the imide moiety is 5,5-diphenyl- B-hydantoinyl.

The control stock (1) is stock A of Table I, supra, to vlfich is added 1 part of prevulcanization inhibitor as o ows:

Stock No.:

1 None.

2 3-(trichloromethylthio)-5,5-diphenyl hydantoin.

3 3-trichloromethyl-2-benzothiazolinone.

4 1-trichloromethylthio-Z-benzimidazolinone.

5 3-trichloromethylthio-2-benzoxazolinone.

The results for Stock No. 1 are the average values obtained from three separately prepared samples.

TABLE XVI Stock 1 2 3 4 Mooney scorch at 121 0.:

The imide moiety may, of course, be formed from two independent radicals as in (A) N-SR where A is acyl derived from a carboxylic acid and R is alkyl, cycloalkyl, or aryl. A is, for example,

0 3. L where R is alkyl, cycloalkyl, or aryl. Similarly, -SR may be the substituent of a simple amide as in a- -sn illustrated in Table XIII or two -SR snbstituents may be present as in AN(SR) Table XVII shows the curing characteristics determined by means of the Rheometer with a stock containing AN-(SRh. The control stock (I) is Stock A of Table I, supra, to which is added 1 part by weight of prevulcanization inhibitor as follows:

Comparable results to those in the tables, supra, illustrating utility are obtained with the inhibitors of this invention which are not illustrated.

Concentration studies show the inhibitors of this invention are effective in rubber at concentrations of 0.05 to 5.0 parts per hundred. Concentrations from 0.10 to 3.0 parts per hundred are preferred.

A wide variety of combinations of Santocure NS and N-(phenylthio)succinimide show storage stability in an eight-week oven aging test at 50 C. These combinations are improved vulcanization accelerators in rubber where: by premature vulcanization is effectively inhibited. Effective inhibitor concentrations for the combinations range from 1 to 9 parts of inhibitor. Comparable results are obtained when other accelerator and inhibitor combinations of this invention are tested for stability.

From the foregoing description, it will be appreciated that in the formula r can be a radical derived by removal of hydrogen from an imide of a dicarboxylic acid. The term imide of a dicarboxylic acid is used in a configurational sense to indicate two carbonyls joined to a single nitrogen, although more than one such configuration may be present in the same molecule. For example, the monoand diimides of benzene tetracarboxylic acid are regarded in the present specification and claims as imides of dicarboxylic acids. The hydrantoins, uracil, and parabanic acid also fall into the category of imides of dicarboxylic acid. The cyclic ureas, by which are meant monocarbonyl cyclic ureas as distinguished from cyclic ureas containing two carbonyls joined to a single nitrogen, present a configuration the reverse of imides of dicarboxylic acids in that only a single carbonyl is present and is joined to two nitrogen atoms. The preferred radicals conforming to are derived from azoles. By azoles are meant the general class of pentatomic heterocyclic ring compounds whether or not unsaturation is present in the ring. Both the imides of dicarboxylic acids and cyclic ureas include pentatomic heterocyclic ring compounds. Other suiatble radicals are derived from monocarbonyl azoles containing one nitrogen atom and one other dilferent hetero atom, for example, sulfur or oxygen, in the ring.

The radicals derived by removal of hydrogen from an imide of a dicarboxylic acid include, for example,

where A is a divalent aliphatic, cycloaliphatic, or aromatic radical. Thus, A is alkylene, cycloalkylene, alkenylene, cycloalkenylene, or arylene. Alkylene radicals belong to the series -C H Alkenylene radicals are olefinically unsaturated aliphatic divalent radicals having the valence on separate carbon atoms, for example, propenylene CH CH=CH--. The corresponding cyclic forms are cycloalkylene, for example, cyclohexylene C H and cycloalkenylene, for example, cyclohexenylene --C H The divalent aromatic radicals are arylene radicals, for example, phenylene. The radicals derived by removal of hydrogen from a monocarbonyl cyclic urea include, for example,

5 A. \C=O where A has the same meaning as before and X is hy- 19 dro en; alkyh'aryl, cycloalkyl, or SR", R ibeingfalkyl, aryl,-orcycloalkyl. v suitable acyclic ureas may berepresentedby the for? mula o d." (w-ii-ame-snm where n, n, and n" are integers, the sum of which is three, it and n being one or two, and n" being zero or one, and R and X having the same meaning as before. It is intended to cover all changes and modifications of the examples of the invention herein chosen for purposes of disclosure which do not constitute departures from the spirit and scope of the invention. The matter contained in each of the following claims is to be read as part of the general description of the present invention.

We claim:

1. A compound of the formula:

A-SR wherein A-is selected from the group consisting of N-maleimidyl, 4 cyclohexene-1,2-dicarboximid-N-yl, bicyclo(2.2.1) hept-5-ene-2,3-dicarboximid-N-yl, 7-oxabicyclo (2.2.1 heptane-2,3-dicarboximid-N-yl, 7 oxabicyclo(2.2.1) hept-S-ene-2,3-dicarboximid-N-yl, alkylbicyclo (2.2.1 hept-5-ene-2,3-dicarboximid-N-yl, N-(arylthio) 1,2,4, 5- benzenetetracarboxylic-1,2:4,5-diimid-N'-yl, N-(alkylthio)-1,2,4,S-benzenetetracarboxylic 1,2:4,5 diimid- Nyl, N-(cycloalkylthio) 1,2,4,5-benzenetetracarboxylic-1,2:4,5-diimid-N-yl, N-hexahydrophthalimidyl and N-succinimidyl and R is alkyl, aryl, cycloalkyl or benzyl,

and wherein cycloalkyl, each occurrence, is cycloalkyl of 5 to 12 carbon atoms in the ring; alkyl, each occurrence, is alkyl of 1 to 20 carbon atoms and aryl, each occurrence, is phenyl, tolyl, ethylphenyl, isopropylphenyl, nitrophenyl, chlorophenyl, or naphthyl providing that R is cycloalkyl when A is N- succinimidyl. 2. A compound according to claim 1 where R is cycloalkyl of 5 to 8 carbon atoms.

3. A compound according to claim 1 wherein A is N-maleimidyl and R is cyclohexyl.

4. N-cyclohexylthio-4-cyclohexene-1,2-dicarboximide.

20 A cI11P1111d i l fisf.. ai9 ..rwh r niA is Nl-heirahyd'rophthalimidyl and R is cyclohexyl.

6. A compound according to claim-1 wherein R is aryl. 7. A compound according to claim 1 wherein A is N-maleimidyl and R is phenyl.

.8. A compound according to claim 1 wherein A is 4-cyclohexene-l,Z-dicarboximid-N-yl and R is phenyl.

9. A compound according to claim 1 wherein R is alkyl of lto 112' carbon atoms.

" 10I'A' compound according to claim 9 wherein R is isopropyl, n-butyl, or n-dodecyl.

1 1-1'; A compound according to claim 10 wherein A is N-maleimidyl and R is isopropyl.

12.'A'compound according to claim 10 wherein A is 4-cyclohexene-1,2-dicarboXimid-N-yl and R is isopropyl. 13. A compound according to claim 1 of the formula wherein A is ethylene and R is cycloalkyl of 5 to 8 carbon atoms.

14. A compound according to claim 13 wherein R is cyclohexyl.

15. A compound according to claim 1 of the formula A-S-R wherein A is selected from the group consisting of 4-cyclohexene-1,2-dicarboximid-N-yl, bicyclo(2.2.1) hept-S- ene-Z,B-dicarboximid N yl,..7-oxabicyclo(2.2..'1) heptane-Z,S-dicarboximid-N-yl, 7-oxabicyclo(2.2. 1 )hept- 5-ene-2,3,-dicarboximid-Nayl, alkylbicyclo(2.2.1 )hept-S- cue-2,3-dicarboximid-N-yl, and N-hexahydrophthalimidyl and R is alkyl, aryl, cycloalkyl or benzyl and wherein cycloalkyl is cycloalkyl of 5 to 12 carbon atoms in the ring, alkyl is alkyl of 1 to 20 carbon atoms and aryl is phenyl, tolyl, ethylphenyl, isopropylphenyl, nitrophenyl, chlorophenyl or naphthyl.

16. A compound according to claim 15 wherein R is benzyl.

References Cited UNITED STATES PATENTS 2,553,770 5/1951 Kittleson 260-3265 S 3,178,447 4/1965 Kohn 260-3265 S 3,285,929 11/1966 .Klauke et a1. 260-3265 S 3,499,030 3/ 1970 Kuhle ct a1 260-3265 S 3,546,185 12/1970 Coran et a1 260-3265 S ALEX MAZEL, Primary Examiner J. TOVAR, Assistant Examiner US. Cl. X.R. 

